Explosive atmospheres can be caused by flammable gases, mists or vapours or by combustible dusts. If there is enough of the substance mixed with air, then all it needs is a source of ignition to cause an explosion.
Explosions can cause loss of life and serious injuries as well as significant damage. Preventing releases of dangerous substances which can create explosive atmospheres, and preventing sources of ignition, are two widely used ways of reducing the risk. Using the correct equipment can help greatly in this.
An explosive atmosphere is defined as a mixture of dangerous substances in the air in the form of gases, vapours, mist or dust, which, under certain conditions of temperature and pressure, has the potential to catch fire and explode.
Many workplaces may contain, or have activities that produce, explosive or potentially explosive atmospheres. Examples include places where work activities create or release flammable gases or vapours, such as vehicle paint spraying, or in workplaces handling fine organic dusts such as grain, flour or wood.
ATEX (ATmospheres EXplosibles in French) is the name commonly given to the two European Directives for controlling explosive atmospheres:
1) Directive 99/92/EC (also known as 'ATEX 137' or the 'ATEX Workplace Directive') on minimum requirements for improving the health and safety protection of workers potentially at risk from explosive atmospheres.
2) Directive 94/9/EC (also known as 'ATEX 95' or 'the ATEX Equipment Directive') on the approximation of the laws of Members States concerning equipment and protective systems intended for use in potentially explosive atmospheres.
International standards IEC 60079 and IEC61241 (IECEx), which are harmonized with EN European Directives, are the main hazardous area standards recognised throughout the rest of the world, outside of Europe.
Employers must classify areas where hazardous explosive atmospheres may occur into zones. The classification given to a particular zone, and its size and location, depends on the likelihood of an explosive atmosphere occurring and its persistence if it does.
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